Lithographic plate made from an n-vinyl-amine and an organic halogen compound dispersed in an hydrophilic colloid



United States Patent 3,374,094 LITHOGRAPHIC PLATE MADE FROM ANN-VINYL-AMINE AND AN ORGANIC HALO- GEN COMPOUND DISPERSED liN AN HY-DROPHILHI COLLOID Eugene Wainer, Shaker Heights, and Harry L. Fichter,

Jr., Lakewood, Ohio, assignors to Horizons Incorporated, a corporationof New Jersey No Drawing. Filed July 19, 1965, Ser. No. 473,238 12Claims. (Cl. 9633) This invention relates to printing plates useful inplanographic and lithographic printing and to the manufacture of sucharticles by a completely dry process utilizing compositions which aresensitive to light. More particularly, the invention relates to thepreparation of planographic or lithographic plates in which a suitablesupport is impregnated or coated with a photosensitive mixture ashereinafter described, then exposed so as to produce a relief image,whereby a plate is produced in which the background iscompletely'hydrophilic in nature and the developed image is oleophilicand hydrophobic.

Since presently known processes for making photographs on lithographicor planographic masters requires swabbing the exposed plate with adesensitizing solution followed by swabbing with a colored lacquer tomake the image visible and to provide strength for the fragile image toinsure long press runsin other words, to give more impressions perplate, it will be readily apparent that a durable printing plate whichdoes not require such swabbing would represent an advance in this art.

A number of United States patents issued to Eugene Wainer and others,describe photosensitive compositions comprising at least the followingconstituents:

(1) An N-vinyl amine,

(2) An organic halogen compound, and

(3) Various optional ingredients, such as a synthetic resin or otherfilm forming material in which the two essential constituents aredispersed or supported.

These patents include the following:

United States Patent 3,042,517, issued July 3, United States Patent3,042,518, issued July 3, United States Patent 3,042,519, issued July 3,United States Patent 3,046,125, issued July 24, 1962; United StatesPatent 3,056,673, issued October 2, 1962; United States Patent3,147,117, issued September 1, 1964.

In addition various improvements thereover are described in copendingUnited States patent applications Serial No. 445,273, filed April 2,1965, claiming the addition of Group V aryl compounds such astriphenylstibine, -arsine, -phosphine or -bismuthine to suchcompositions, and Serial No. 398,097, filed September 21,

1964, claiming the use of mercaptobenzothiazole in such compositions.The disclosures in these applications are incorporated herein byreference.

As noted above, the use of N-vinyl compounds for preparing photopolymerimages with halogen containing hydrocarbons as the activating source offree radicals is extensively described in the above noted patents ofEugene Wainer. These patents describe the use of compounds such asN-vinyl carbazole and carbon tetrabromide used with plastic bindersdissolved in organic solvents and coated on a suitable support such aspaper, glass or plastic films. The plastic binders described in thepatents noted are completely hydrophobic in character and will nottolerate water in any form. With such compositions the image which isdeveloped out by heating will accept ink-both in the background and theimage areas when placed on a press. The resulting completely inkedmaster is therefore totally unsuited to use as a planographic orlithographic master. The present invention resides in the use ofhydrophilic colloidal binders for 3 ,3 74,094 Patented Mar. 19, 1968compositions of the type already known whereby they can be coated onpaper or metal supports to give uniform coatings without separation ofthe aqueous or the oleo phase.

When modified in this manner, i.e. by the inclusion of a hydrophilicbinder in the photosensitive compositions the image formed on exposureto light followed by mild heating for development and fixing isreceptive to greasy lithographic inks and repels the aqueous fountainfluid. The background material is completely hydrophilic in nature andtherefore is Wetted by the aqueous fountain fluid and repels the greasyink leaving a clean white background. The oleophilic image which picksup the ink, transfers the ink in the pattern of the image to a rubberblanket which in turn transfers it to the paper feed and repeated copiesare printed by this offset procedure.

The invention provides a planogra-phic or lithographic master with aphotographic image based on the photopolymerization of N-vinyl compoundsusing halogenated hydrocarbon activators, all active constituents beingcoated on paper in a hydrophilic binder. The resulting coating isexposed to visible light through a photographic negative, mask, stencilor other similar subject. The exposed print contains a latent imagewhich is made visible by mild heating. During the course of heating theunreacted volatile activator is driven off and the print becomes fixedas development occurs. The developed and fixed print is then mounted onan off-set press as a lithographic master and copies printed from it.Both halftone and line negatives may be used in preparing these masters.The process is completely dry. No solutions are needed to produce theimage or to prepare the desired printing plate.

One object of this invention therefore is to prepare lithographicmasters with photographic images without any need whatever for wetprocessing such as desensitizing or lacquering. After exposure followedby heat development the master contains a relief image which isimmediately ready for the press.

Other objects will become apparent from the description which follows inwhich preferred embodiments are disclosed by way of illustration whichare not intended to be construed as limiting the invention.

In general the ingredients of this invention are brought together usingthe following technique: the N-vinyl carbazole or other suitable N-vinylamine, and the CBr or other halogen containing activators described inthe patents listed above, are dissolved in a suitable solvent such ascyclohexanone or toluene. The resulting solution is added to a watersolution of the hydrophilic colloidal binder material preferablycontaining a suitable wetting or dispersing agent and the mixture isplaced in a Waring blender and blended until a stable emulsion isformed. Emulsions made in the manner described have been found to bestable through weeks of standing without any sign of separation of theoil and water phases. In addition to the above-mentioned ingredients,the solution added to the colloidal binder should contain asulfurcontaining organic compound such as mercaptobenzothiazole forimprovement of the photographic speed of the coated emulsion. Thesolution should also include a triphenyl derivative of phosphorus,arsenic, antimony or bismuth. The presence of these triphenyl compoundsplus suflicient heating after exposure to insure development insures aclean white 'unfogged background, but a more important reason for theincorporation of the triphenyl Group V compounds in the compositions isto provide a slight relief image after the heat treatment.

Although paper is one preferred substrate to which the photosensitivecomposition is applied, another and a particularly preferred platematerial is aluminum having 'at least one surface anodized so that itbears a porous absorbent oxide film into which the photosensitivecomposition can be readily impregnated.

Having described the composition of this invention in general terms thefollowing is a more detailed description of the specific ingredientsemployed and the manner in which they may be compounded. For simplicity,representative members of each group of ingredients are listed by way ofillustration in the tables which follow. It will be understood thatother similar materials may be used without departing from the intendedscope of the invention. The hydrophilic colloids which are suitable foruse in this invention may be any of the natural colloids, such asstarches, gums, polysaccharides and protein material such as casein orthey may be synthetic materials such as polyvinyl alcohol, methyl vinylether/ 'maleic anhydride copolymers, carboxymethyl cellulose and othersynthetic derivative of cellulose. Table I lists the hydrophiliccolloids suitable for this invention and gives a recommended range ofconcentration for the colloid in water.

Table I.-Hydrophilic colloids Recommended conc.

Table H.-Suitable solvents for dissolving photosensitive elements fordispersion in the protection colloid Solvent: Boiling point, C. Benzene80.1 Cyclohexane 80 Cyclohexanone 155 Toluene 111 Xylene 144 Table IIITriphenylphosphine Triphenylstibine Triphenylbismuthine TriphenylarsineTable IV Mercaptobenzothiazole (Mencaptobenzoic acidPhenylmercaptotetrazole Ethyl mercaptotetrazole Methyl mereaptotetrazoleAll of the materials listed in Table I were found to be useful asprotective hydrophilic colloids in the practice of this invention. Some,however, gave longer and some gave shorter press runs but all exhibitedthe desired property necessary to this invention, that is, there was aneffective rejection of ink in the non-image background and an acceptanceof ink in the hydrophobic image area. The range of composition listed inthe table are the extremes of a working range. Best results wereobserved when the concentration of colloidal binder was about midwaybetween the extremes listed.

In order to provide a practical stability to the emulsion with the abovehydrophilic colloids, it is necessary to include an emulsifying orwetting agent in the formulation. Hundreds of emulsifying agents areavailable commercially and many of them have been successfully employedin the preparation of emulsions for the practice of this invention,including the following wetting agents: the non-ionic agent TritonX-100, an alkyl polyether alcohol from the Rohm & Haas Company, theanionic wetting agent Tergitol No. 7 which is sodium heptadecyl sulfatefrom the Union Carbide Corporation or Nacconol, an alkyl aryl sodiumsulfonate from the National Aniline Div. of the Allied Chemical and DyeCorporation or Nekal, a sodium alkyl naphthalene sulfonate from theGeneral Aniline and Film Corporation.

The recommended concentration of emulsifying agent is 1 to 3 percent ofthe total volume of liquid in the final emulsion.

Suitable solvents for dissolving the N-vinyl carbazole and the halogencontaining activators 'are listed in Table II. Boiling point of thesolvent is an important consideration in its choice. If the boilingpoint of the solvent is too low and its volatility is too high it willflash off from the drying surface of the coating leaving an irregularsurface. If on the other hand the boiling point of the solvent is toohigh and its volatility too low, the solvent will never evaporate fromthe coated mixture and a sticky, gummy layer remains on the surface. Thesolvents listed in the table have been found to give excellent dryingconditions resulting in smooth, even, non-sticky coatings. Water may beadded to the final emulsion so as to control its viscosity and make itmore easily coated on the receiving sheet. This may be controlled tosome extent by using a more dilute solution of the hydrophilic colloidalbinder but if the viscosity of the colloidal binder is too low, theemulsion will not remain stable and separation will occur. It has beenfound preferable to use a higher concentration of binder and to diluteafter the emulsion has been prepared.

It will be understood that all mixing, coating and drying of thephotosensitive mixture is carried out under red safelight conditions.

The following examples are indicative of the method of practicing thisinvention, it being understood that the invention is illustrated by butnot limited by the following examples:

EXAMPLE I Ten cc. of a 7% aqueous solution of polyvinyl alcohol (Elvanolgrade 72-60) was added to a Waring Blendor, then one cc. of Triton X-(Rohm & Haas) and ten cc. of water were added. A solution consisting of10 cc. of cyclohexanone, 160 mg. of mercaptobenzothiazole, 320 mg. oftriphenylstibine, 6.4 grams carbontetrabromide, and 8 grams of N-vinylcarbazole was prepared and after complete solution was attained thecyclohexanone solution was added to the Elvanol solution in the WaringBlendor. The contents were blended together thoroughly for 60 seconds.The resulting emulsion was coated on gr. baryta paper at a coatingthickness of .0015-inch wet. The dried coating was exposed through aphotographic negative to a photoflood lamp, exposure time being 15 to 60seconds depending on the quality of the negative and the distance fromthe lamp. The exposed paper Was heated carefully under an infrared lampfor a period of 30 to 90 seconds, depending upon the length of exposureto the photoflood lamp and the distance from the heating lamp. Theinfrared heating developed and simultaneously fixed the exposed master.After the infrared heating the sample was mounted on a press such as aDitto or an Addressograph-Multigraph duplicating offset press andimpressions made in the manner normally prescribed for the use of theparticular machine. Excellent reproductions of the master were made andno sign of deterioration of the master was observed after 500 copies.

EXAMPLE II In this example the polyvinyl alcohol used in Example I wasreplaced with poly(methyl vinyl ether-maleic anhydride). A aqueoussolution was used, and similar results were obtained.

EXAMPLE III Identical to Example I except that half of hydrophilic resinwas polyvinyl alcohol and half was the poly (methyl vinyl ether-maleicanhydride). The master was similar to that obtained in Example I.

EXAMPLE IV The same as Example I except a 5% aqueous solution ofpolyacrylamide was used in place of polyvinyl alcohol. Thepolyacrylamide used was sold under the trade name Cyanamer Grade P26 bythe American Cyanamid Corporation.

EXAMPLE V The same as Example I except polyvinyl pyrollidone was used inplace of polyvinyl alcohol. Polyvinyl pyrollidone is a product of theGeneral Aniline and Film Corporation; Grade K30 was used in 5%concentration.

EXAMPLE VI The same as Example I except that 2.5% aqueous solution ofmethyl cellulose (Methocel, Dow Chemical Company) was used in place ofpolyvinyl alcohol.

EXAMPLE VII The same as Example I except a 20% aqueous solution of gumarabic is used in place of polyvinyl alcohol.

The printing plates produced in Examples IV through VII were found to besuitable for planographic printing and lithographic printing.

As in the compositions described in the Wainer patents the organichalogen compound is one represented by the general formula A-C-X whereineach X is a chlorine or bromine atom and A represents either H, alkyl,haloalkyl, aroyl, aryl, substituted aryl, or bromine or chlorine atom.

The relative proportions of N-vinyl amine and organic halogen compoundis between 10 and 200 parts of N-vinyl amine for each 100 parts oforganic halogen compound and the amount of hydrophilic binder relativeto the remainder of the composition is in the range of 10 to 100 partsof binder per 100 parts of the remainder of the composition.

The amount of Group V aryl compound necessary to produce the desiredrelief image is between about .625 and 6.25 parts per 100 parts byweight of N-vinylcarbazole or other N-vinyl amine.

EXAMPLE VIII The composition of this example was prepared under a redsafelight as in Example 1. Again, under red safelight conditions thecoated photosensitive material is calendered at high pressure in whichthe pressure applied by the rolls is in the range of 10,000 lbs. persquare inch at the nip up to 25,000 lbs. per square inch, the rolls usedbeing polished bright chrome plated. Under these conditions at verybright, glossy surface is obtained. Exposure time under the conditionsdescribed in Example I are reduced by a factor of 5, namely to a rangeof 3 to 12 seconds as against the 15 to 60 seconds presently cited inExample I. The advantage of this calendering operation other thanphotographic speed is to increase the life of a master with respect tohigh quality reproduction by at least a factor of 5 and generally up toa factor of 10.

EXAMPLE IX Paperboard stock is coated with a mixture of 100 parts ofpapermakers clay, 18 parts by weight of a 50 percent polyvinylacetateemulsion in water, and 2 parts of isolated soya protein which has beentreated with 12 percent by weight of ammonium hydroxide, 20 parts byweight of water are added to the mixture which is then coated onpaperboard stock with a doctor blade, dried at C., and then calenderedon polished rolls which leaves a highly glossy surface. A solutionconsisting of 10 cc.s of cyclo' hexanone, 160 milligrams ofmercaptobenzothiazole, 320 milligrams of triphenylstibine, 6.4 grams ofcarbon tetrabromide, 8 grams of N-vinylcarbazole, and 1 cc. of TritonX-l00 (Rohm & Haas) was prepared and applied to the surface of thecalendered stock by roll coating yielding a wet thickness ofapproximately 0.002" in thickness. The photosensitive solution wasprepared under red safelight conditions and the application to the basestock and subsequent drying at 50 C. also carried out under redsafelight conditions. After drying the stock was again calendered andagain a long-life plate was obtained Whose photographic speed wasroughly 5 times that of a comparable emulsion type of coating. Theamount of isolated soya protein utilized in the baseboard may be variedfrom 1 part to 10 parts per parts of papermakers clay and the amount ofpolyvinylacetate emulsion may be varied from 10 parts to 30 parts per100 parts of papermakers clay. Casein or polyacrylamide may besubstituted pound for pound for the isolated soya protein.

tion of polyacrylamide in water at 0.003" thickness, al

lowed to dry and calendered. Under darkroom safelight conditions thissurface is then coated. with a solution consisting of 25 cc.s ofbenzene, milligrams of mercaptobenzothiazole, 320 milligrams oftriphenylstibine, 6.4 grams of carbon tetrabromide, and 8 grams of N-vinylcarbazole, and 1 cc. of Triton X-lOO (Rohm & Haas), the coatingbeing applied by dip-coating methods to achieve a wet film thickness of0.0015". After drying under safelight conditions the composite is againcalendered under equivalent safelight conditions after which thephotosensitive material is ready for exposure, heat development and useas a lithographic master.

The calendering variation thus provides the possibility for combining anotherwise hydrophobic composition with a hydrophilic base so as to yieldoverall hydrophilic characteristics without the use of emulsiontechnology until the photosensitive material has been properly exposedand heat developed.

EXAMPLE XI The composition of Example I was applied to the surface of ananodized aluminum plate and a satisfactory lithographic plate resultedfrom the exposure and development as described in Example I.

Other substrates which can be used with the previously describedemulsions include paper coated with polypropylene, a polyethyleneterephthalate and polyester subbed with polyvinyl butyrate.

Example IX illustrates the use of a hydrophobic binder in thisinvention. Polyvinylacetate dissolved wholly in an organic solvent anddried to a film is hydrophobic in character. However, if thepolyvinylacetate is prepared as a water emulsion in the presence of anemulsifying agent and further protected by means of a small amount of aprotective colloid such as a soya protein or casein then thepolyvinylacetate composition which develops from such an emulsion ishydrophilic in character. It appears that particles of polyvinylacetatein the emulsion are coated, in all probability, either with hydrogenions or with hydroxyl ions which impart the hydrophilic characteristics.The difference as to whether polyvinylacetate is laid down in an organicsolution or from a protected colloid type of water emulsion is quitestriking.

We claim:

1. A dry photosensitive plate useful in the preparation of aphotolithographic master comprising at least one of each of thefollowing constituents:

(1) an N-vinylamine;

(2) a halogen containing compound in which at least three halogen atomsare linked to a single carbon atom, each of said halogen atoms beingselected from the group consisting of Br and Cl;

(3) a triaryl compound of an element selected from the group consistingof P, Bi, Sb and As;

said constituents being dispersed in and supported by a hydrophilicbinder containing a minor amount of an emulsifying agent.

2. The plate of claim 1 wherein the composition includes (4) at leastone sulfur containing organic compound in which the sulfur is linkeddirectly to a carbon atom.

3. The plate of claim 1 supported on a flexible substrate.

4. A photosensitive printing plate useful in planographic andlithographic photolithography having image and ink receptive areascomprising an N-vinylamine and a halogen containing hydrocarbon, thenon-image and ink repelling areas having been rendered hydrophilic bythe use of a hydrophilic binder for said N-vinylamine and said halogencontaining hydrocarbon and said image areas having been renderedrelieved from the surface of said plate by incorporation of a Group Vtriaryl compound of an element selected from the group consisting of P,Bi, Sb and As in said areas, the plate being prepared for use byimagewise exposure to light followed by heat development.

5. A dry printing plate useful in planographic and lithographic printingcomprising the photochemical reaction products available from animagewise exposure of a mixture of an N-vinylamine, a halogen containinghydrocarbon, a Group V triaryl compound, a sulphur containing organiccompound in which the sulphur is linked directly to a carbon atom,dispersed through the medium of an emulsifying agent in a hydrophilicbinder, in which the image and ink receptive areas are produced inrelief as a consequence of exposure of the plate to light on animagewise basis followed by blanket development with infrared light andheat, and the areas which have not been previously exposed to light areink repellent, the distinction between image and ink receptive areas andnon-image and ink repellent areas having been made permanent by theinfrared and heat development step.

6. A dry printing plate useful in planographic and lithographic printingcomprising the photochemical reaction products available from animagewise exposure of a mixture of an N-vinylamine, a halogen containinghydrocarbon, a Group V triaryl compound, dispersed through the medium ofan emulsifying agent in a hydrophilic binder, in which the image and inkreceptive areas are produced in relief as a consequence of exposure ofthe plate to light on an imagewise basis followed by blanket developmentwith infrared light and heat, and the areas which have not beenpreviously exposed to light are ink repellent, the distinction betweenimage and ink receptive areas and non-image and ink repellent areashaving been made permanent by the infrared and heat development step.

'7. A method of preparing a photolithographic plate which comprises:

(1) applying a liquid composition to a support under darkroomconditions, said composition comprising at least one of each of thefollowing constituents:

(a) an N-vinylamine (b) an organic halogen compound in which at leastthree halogen atoms are linked to a single carbon atom, each of saidhalogen atoms being selected from the group consisting of Br and Cl (c)a triaryl compound of an element selected from the group consisting ofP, Bi, Sb and As (d) a hydrophilic film forming binder (e) a volatileliquid vehicle for said constituents and (2) drying the resulting coatedarticle under darkroom conditions to produce a photosensitive plate.

8. The method of claim 7 including in addition the incorporation of atleast one sulfur containing organic compound in which the sulfur islinked directly to a carbon atom in said composition.

9. The method of claim 7 wherein the liquid composition includes inaddition a minor amount of emulsifying agent and the composition isemulsified before it is applied to the support.

10. The method of claim 9 in which the plate is calendered after thecomposition is dried but before imagewise exposure.

11. A method of photolithography which comprises preparing a dryphotosensitive plate by the method of claim 7 and then photographicallyexposing said plate followed by exposing the entire surface of saidplate to infrared and heat, thereby producing a relief image thereon andrendering said image permanent.

12. A method of photolithography which comprises preparing a dryphotosensitive plate by the method of claim 10 and then photographicallyexposing said plate followed by exposing the entire surface of saidplate to infrared and heat, thereby producing a relief image thereon andrendering said image permanent.

References Cited UNITED STATES PATENTS 2,882,262 4/1959 Smith et al.96-115 X 3,046,125 7/1962 Wainer 96-35 3,065,160 11/1962 Levinos et al96l15 NORMAN G. TORCHIN, Primary Examiner.

R. E. MARTIN, Assistant Examiner.

7. A METHOD OF PREPARING A PHOTOLIGHOGRAPHIC PLATE WHICH COMPRISES: (1)APPLYING A LIQUID COMPOSITION TO A SUPPORT UNDER DARKROOM CONDITIONS,SAID COMPOSITION COMPRISING AT LEAST ONE OF EACH OF THE FOLLOWINGCONSTITUENTS: (A) AN N-VINYLAMINE (B)AN ORGANIC HALOGEN COMPOUND INWHICH AT LEAST THREE HALOGEN ATOMS ARE LINKED TO A SINGEL CARBON ATOM,EACH OF SAID HALOGEN ATOMS BEING SELECTED FROM THE GROUP CONSISTING OFBR AND CL (C) A TRIARYL COMPOUND OF AN ELEMENT SELECTED FROM THE GROUPCONSISTING OF P, BI, SB AND AS (D) A HYDROPHILIC FILM FORMING BINDER (E)A VOLATILE LIQUID FOR SAID CONSTITUTENS AND (2)DRYING THE RESULTINGCOATED ARTICLE UNDER DARKROOM CONDITIONS TO PRODUCE A PHOTOSENSITIVEPLATE.